The foundation of this revised competitive resubmission of the Early Indicators of Later Work Levels, Disease and Death (El) program project is the discovery in 2004 that disparities in health and mortality across the wards of the major US cities in 1900 were not only far greater (on the order of 10-to-1) than recognized, but that 84% of the disparities between the worst and best wards had diminished by 1950. When the analysis was pushed back into the 19th century, it was discovered that young adult death rates in the 17 largest cities of 1860, when analyzed longitudinally, were far higher than previously revealed by period life tables. Union Army (UA) recruits from these cities who survived the Civil War had die off rates so high that their experience is characterized by life tables with eo of about 28.6 years, which is about 17.7 years less than life expectancy in rural areas. The explanation of the disparity within and across cities, as well as across rural areas, and the social, economic, and biodemographic factors that lead to the amelioration of these disparities between 1830 and 1950 requires the creation of a data set with ecological variables capable of explaining the process. The collection and management of these data account for three-fourths of the cost of this program project. Four analytical projects initiate the analysis of the new data: Project 1 will analyze how the socioeconomic and health status of UA soldiers and veterans interacted with each other over the life course, stressing interactions across different sub-populations and times. Project 2 focuses on those veterans who lived to be age 95 or older (the last 2% of the cohort) comparing their aging processes with those born just before World War I and investigating whether the effects of earlier life environmental stress persist even to very old ages. Project 3 analyses the impact of exposure to severe within urban environments over different spans of the life course on the process of aging. Project 4 deals with the differences across urban and rural areas in the process of aging. RELEVANCE: This project bears on the explanation for the marked decline in US age-specific morbidity and mortality rates over the 20th century. It assesses the relative contribution of the decrease in disparities in environmental conditions to long-term improvement in health and longevity in the US and other rich nations and in the Third World. It also provides a basis for forecasting the impact of life-cycle improvements in health experienced by parents and grandparents of baby-boom and baby-dearth generations on the health of their progeny and some likely changes in the process of aging in the first half of the 21st century.